Aqueous polymer dispersions

Abstract

Phosphorus-containing aqueous polymer dispersions and the use thereof as binders in coating formulations.

The invention claimed is: 
     
       1. A process for producing an aqueous polymer dispersion by free-radically initiated aqueous emulsion polymerization, the process comprising:
 (i) free-radically polymerizing, in an aqueous medium in the presence of at least one phosphorus-containing dispersing aid, in a first polymerization stage (polymerization stage 1), 
 ≥1.0 and ≤3.0% by weight of at least one α,β-monoethylenically unsaturated C 3 - to C 6 -mono- or -dicarboxylic acid (monomers A1), 
 ≥1.5 and ≤6.0% by weight of at least one ethylenically unsaturated compound comprising at least one phosphorus-containing group (monomers A2), and 
 ≥91.0% and ≤97.5% by weight of at least one ethylenically unsaturated compound distinct from the monomers A1 and A2 (monomers A3), 
 wherein the amounts of the monomers A1 to A3 sum to 100% by weight (total monomer amount 1), to obtain a polymer 1; and, subsequently, 
 (ii) free-radically polymerizing, in the presence of the polymer 1, in a second polymerization stage (polymerization stage 2), 
 ≤0.1% by weight of at least one α,β-monoethylenically unsaturated C 3  to C 6 -mono- or -dicarboxylic acid (monomers B1), 
 ≤0.1% by weight of at least one ethylenically unsaturated compound comprising at least one phosphorus-containing group (monomers B2), and 
 ≥99.8% and ≤100% by weight of at least one ethylenically unsaturated compound distinct from the monomers B1 and B2 (monomers B3), 
 wherein the amounts of the monomers B1 to B3 sum to 100% by weight (total monomer amount 2), to obtain a polymer 2, 
 with the proviso that 
 a glass transition temperature Tg 1  of the polymer 1 is ≥−5° C. and ≤10° C., 
 a glass transition temperature Tg 2  of the polymer 2 is ≥10° C. and ≤40° C. and is at least 10° C. above the glass transition temperature Tg 1 [Tg 2 =Tg 1 +≥10° C.], 
 a ratio of the total monomer amount 1 to the total monomer amount 2 is 70% to 85% by weight to 15% to 30% by weight and 
 an amount of the at least one phosphorus-containing dispersing aid is ≥0.5% by weight based on a sum of the total monomer amount 1 and the total monomer amount 2 (total monomer amount). 
 
     
     
       2. The process of  claim 1 , wherein the monomers A1 are acrylic acid, methacrylic acid, itaconic acid, fumaric acid, maleic acid and/or crotonic acid. 
     
     
       3. The process of  claim 1 , wherein the monomers A2 are vinylphosphonic acid and/or a (meth)acryloxy(poly)alkoxy phosphate. 
     
     
       4. The process of  claim 1 , wherein the monomers A3 are to an extent of ≥80% by weight selected from the group consisting of n-butyl acrylate, n-butyl methacrylate, 2-ethylhexyl acrylate, styrene and methyl methacrylate. 
     
     
       5. The process of  claim 1 , wherein no monomers B1 and B2 whatsoever are employed. 
     
     
       6. The process of  claim 1 , wherein the polymerization stages 1 and 2 are performed at a pH in a range of from ≥3 to ≤8 measured at room temperature. 
     
     
       7. The process of  claim 6 , wherein a pH adjustment is carried out with a base having a boiling point ≤20° C., measured at 1.013 bar (absolute). 
     
     
       8. The process of  claim 1 , wherein the monomers A3 are to an extent of >0% and ≤20% by weight selected from the group consisting of 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-(acetoacetoxy)ethyl methacrylate, 2-ureidoethyl methacrylate, diacetone acrylamide, glycidyl methacrylate, 3-(methacryloyloxy)propyltrimethoxysilane, vinyltriethoxysilane, allyl methacrylate and 1,4-butanediol diacrylate.